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50 gallon Rheems piped in series...

01-12-2009, 02:35 PM

The second one is not working! (Both WH were installed at the same time and are almost nine years old.) I always thought the first one goes out because it works the hardest. Basically here is the scenario:

Ever since the H/O has lived in the house, the second one's temp has always been set hire than the first. My last visit I informed her that the temp on the second should be reduced. She turned it down to 120. Then they had problems with hot water. I measured the powder room and only got 111. I measured the laundry tub next to the heaters and got 113. I then ran the hot water until there was only cold coming from the first into the second. Guess what? The first burner turned right on and began heating the incoming water. The second burner never even turned on! It was set at 130! I then manually turned up the thermostat and it then began to fire. Bad thermostat? I think so. I gave her prices, and if she calls me to do the work, I informed her I would pipe them in paralell (sp) if replaced.

The second one is not working! (Both WH were installed at the same time and are almost nine years old.) I always thought the first one goes out because it works the hardest. Basically here is the scenario:

Ever since the H/O has lived in the house, the second one's temp has always been set hire than the first. My last visit I informed her that the temp on the second should be reduced. She turned it down to 120. Then they had problems with hot water. I measured the powder room and only got 111. I measured the laundry tub next to the heaters and got 113. I then ran the hot water until there was only cold coming from the first into the second. Guess what? The first burner turned right on and began heating the incoming water. The second burner never even turned on! It was set at 130! I then manually turned up the thermostat and it then began to fire. Bad thermostat? I think so. I gave her prices, and if she calls me to do the work, I informed her I would pipe them in paralell (sp) if replaced.

I'd have to see it to completely understand. But if you ran water until the first one became "cold" and fired, the second one would not and should not fire for a little while depending on how much water you're running at the time.

When the first one begins firing and goes warm/cool on the outlet the second one is basically like a full temperature heater where a fixture hasn't been turned on yet. On top of that you have the first heater/burner firing the incoming water to the second. So it can be a pretty good delay before the cooler incoming temp hits the thermostat causing the second one to fire. Once again depending on water turnover. There may be nothing wrong.

J.C.

Comment

I ran the first till it was cold, and I kept it running. The second is set at about 130 degrees. At the laundry tub next to the WH's I tested the temp and the max I got was 113 degrees. The 2nd burner should have been lit by this time.

The cold water from the first ran into the second for about 10 minutes. Surely, it should have fired.

Being relatively close, I plan to stop by when the heaters are idle, and take a temp from both boiler drains.

Comment

I know that you probably don't want to repair the heaters, but i would suspect a possible bad dip tube in heater 2. That is if it will maintain temp at all. If it just never fires, then of course you have a bad thermostat, but if you are dumping cold water on top of heater it could be difficult to trigger thermostat! Just a thought.

Comment

Good point. I want to test the temp when the heaters have been idle. Dip or no dip, it should be 120 if the thermostat works. Being 8 years old, I find it hard to justify the $200 to replace it. Of course if you have not got the money. Thanks all!

Comment

Keep in mind that the stats in any two WHs are not calibrated and even though you set them both to say 130 that does not mean they will both trip on at 130, there could be as much as +/- 5 degrees difference.

"When we build let us think we build forever. Let it not be for present delight nor for present use alone. Let it be such work that our descendants will thank us for, and let us think, as we lay stone upon stone, that a time is to come when these stones will be held sacred because our hands have touched them, and that men will say, as they look upon the labor and wrought substance of them, "See! This our fathers did for us."
John Ruskin (1819 - 1900)

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i wouldnt pipe them in parallel because this will cut there hot water availability in half unless you use balance valves and balance the system. water will follow the path of least resistance.. or u could use a reverse return piping method

Comment

Well, I replaced these two 50 gallon water heaters last Thurs. I piped them in series at the request of the owner. She had nothing but praise the next day when I came to do some more work, unrelated to the water heaters.

Last night she called and told me she filled her soaker tub and could not fill it all the way because she ran out of hot water. She said it got about a quarter full, and then it got cold.

So I just got back from her house.

Both water heaters were idle when I arrived. Each set at 120. I went up to the 2nd floor and began filling the tub. I filled it a little over a quarter and the temp remained at 119-118. After reaching that point, the temp would very slowly decline. I would estimate the tub to be about 3/4 full and the last temp was 99-98 degrees.

A couple points:
-both water heaters appear to functioning correctly.
-I dont know the exact capacity of the soaker tub.

I will check back with her tomorrow. I have a feeling she is going to count how many gallons it takes to get to the 1/4 mark. I ran out of time, as I was going to get some tub dimensions.

What do I think? Before her water heaters went bad, the first was at 120, the second 130. I think this 10 degree difference, gave her the edge that is lost now. Both heaters have the same specs as the old ones, just a different brand.